Toán Lớp 8: Đề bài: Khai triển biểu thức
a) (2x+y)^2
b) (2-xy)^2
c) (3x-2y) (3x+2y)
d) 2 (x^2 +1/2y) (2x^2 -y)
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Toán Lớp 8: Đề bài: Khai triển biểu thức
a) (2x+y)^2
b) (2-xy)^2
c) (3x-2y) (3x+2y)
d) 2 (x^2 +1/2y) (2x^2 -y)
Comments ( 2 )
a)(2x+y)²
=(2x)²+2.2xy+y²
=4x²+4xy+y²
b) (2-xy)²
=2²-2.2xy+(xy)²
=4-4xy+x²y²
c)(3x-2y)(3x+2y)
=(3x)²-(2y)²
=9x²-4y²
d)2(x²+$\frac{1}{2}$y) (2x² -y)
=(2x²+y)(2x² -y)
=(2x)²-y²=4x²-y²